In vitro activities of three carbapenems against recent bacterial isolates from severely ill patients at Swedish hospitals

To study the in vitro activity of imipenem, meropenem and ertapenem against common pathogens isolated from patients in intensive care, haematology and dialysis/nephrology units at 7 Swedish university hospitals, a total of 788 isolates were collected during 2002-2003. The distribution of the isolates was as follows: Escherichia coli (n = 140), Klebsiella spp. (n = 132), Proteus spp. (n = 97), Enterobacter spp. (n = 113), Pseudomonas aeruginosa (n = 126), Acinetobacter spp. (n = 53) and Enterococcus faecalis (n = 127). The susceptibility to the 3 carbapenems was determined by E-test, and the MICs were interpreted according to SRGA criteria. All 3 carbapenems were highly active against Enterobacteriaceae. The overall susceptibility to imipenem, meropenem and ertapenem was 90%, 98% and 93%, respectively. Against Enterobacteriaceae, Enterobacter spp. excluded, ertapenem had an equal or lower MIC90 than meropenem. Apart from being the most active carbapenem against Enterobacteriaceae, meropenem was also the most active carbapenem against P. aeruginosa, whereas imipenem was the most active drug against Acinetobacter spp. The carbapenems are still potent antibiotics. With the introduction of ertapenem, and an expected increase in the carbapenem consumption due to an increased prevalence of strains with extended-spectrum beta-lactamases, continuous surveillance of carbapenem resistance appears to be warranted, with special attention to P. aeruginosa, Enterobacter and Proteus spp.